1. Field of the Invention
This invention relates to a seal device or an air sealing device for use in the flange mating surfaces of a vacuum container, particularly, a low pressure exhaust chamber of a steam turbine for use in a boiling water type nuclear reactor.
2. Description of the Prior Art
Hitherto, a low pressure exhaust chamber of a steam turbine for use in a boiling water type nuclear reactor is split into segments due to the limitations arising from the viewpoints of machining, transportion, assembly and disassembly, so that there have to be used many flanges which are to be jointed on their mating surfaces. However, complete sealing may not be achieved for flange mating surfaces which overlap each other to a cross pattern. this necessitates the use of a special device such as an air extractor and a vacuum pump for extracting air from the low pressure exhaust chamber.
However, in a boiling water type, nuclear reactor power plant, steam produced in the nuclear reactor possibly contains a very small amount of radioactive non-condensive vapor, as the case may be, so that such steam may be possibly mixed with air flowing into the container, thus presenting a source of a great amount of polluted vapor. The production of such polluted vapor then dictates the use of an excessive or unwanted device for treating the vapor thus polluted.
Recently, a rare gas hold-up apparatus has been adopted for treating polluted vapor. However, this type apparatus is massive, while the capacity thereof is governed by the amount of air to be taken in the low pressure exhaust chamber. Accordingly, for rendering smaller the size of this massive apparatus, it is imperative to reduce the amount of air being taken in the low pressure exhaust chamber.